Vibration Isolation

ABSTRACT

Systems and apparatuses are described for reducing shock and vibration experienced by a payload. In embodiments, a slender element, such as a blade made of spring steel, in its post-buckled state, supports or connects to a payload and reduces vibration effects on the payload. In embodiments, systems and apparatuses using buckled elements isolate or otherwise mitigate the effects of shock and/or vibration on a payload from forces in the vertical direction (i.e. the direction in line with the gravitational force), from forces in the horizontal direction, or both.

BACKGROUND

A. Technical Field

The present invention pertains generally to minimizing or isolating theeffects of shock and/or vibration on an object (which includes withoutlimitation, storage systems, electronic devices, mechanical devices,electro-optical devices, instruments, tools, equipment, and otheritems), and relates more particularly to systems and apparatuses forreducing vibration effects on a payload.

B. Background of the Invention

Many storage systems, electronic devices, instruments and otherequipment are sensitive to vibrations and cannot operate correctly whenexposed to excessive vibration levels. Environments that are especiallysusceptible to excessive vibration include mobile platforms such asaircraft, automotive vehicles and other vessels.

To improve the performance, to extend the operating life, and/or toimprove the operating efficiency of such objects in environments wheremotion noises effects are present, vibration isolators are used toreduce the vibrations experienced by the object. Current vibrationisolation products often rely on visco-elastic materials (such as rubberand rubber-like compounds), coils, or conventional springs to providethe vibration isolation for such equipment. These products havelimitations which leave room for improved vibration isolation systemsbased on other technologies.

SUMMARY OF THE INVENTION

Systems and apparatuses are described for reducing unwanted motion to apayload. It shall be understood that unwanted motions from vibrationsshall be construed to mean vibration, shock, or both.

An aspect of the present invention is the use of constraints inconnection with Euler springs to reduce unwanted motion. In embodiments,a system for reducing vibrations of a payload includes a payload mountand at least one Euler spring. The Euler spring is configured to connectat one end to the payload mount, and its other end is configured to becoupled to a supporting structure. The Euler spring is constructed to bein a post-buckled state that reduces vibrations of a payload attached tothe payload mount by displacing. The system also includes one or moreconstraints configured to contact at least a portion of the Euler springbetween the first and second ends of the Euler spring during adisplacement stage of the Euler spring. The constraints may beconfigured to contact different Euler springs, different positions of anEuler spring, and/or contact at different displacement stages. Inembodiments, a constraint may be configured to produce a non-linearspring behavior in the Euler spring.

In embodiments, vibration isolation systems may include a compensationsystem. The compensation system may comprise a sensor that detects acharacteristic related to motion, (such as position, velocity, oracceleration), a compensator that provides an output that is at least inpart based upon a detection from the sensor, and an actuator that,responsive to the output provided by the compensator, alters aconfiguration of a constraint. The configuration of the constraint thatmay be altered includes its position relative to the Euler spring andits shape. In embodiments, the constraint may be configured to affect anangle of departure of at least one of the first and second ends of anEuler spring.

Embodiments of systems for reducing vibration effects on a payloadinclude controllably altering one or more of the angle of departures ofthe ends of one or more Euler springs. For example, in embodiments, asystem for reducing vibrations of a payload includes a payload mountconnected to a first mounting connector and an Euler spring with itsfirst end connected in a fixed position relative to the first mountingconnector forming a first angle of departure of the Euler spring, andthe Euler spring's second end connected in a fixed position relative toa second mounting connector forming a second angle of departure of theEuler spring. In the embodiments, at least one of the first and secondmounting connectors is controllably alterable to change the angle ofdeparture associated with the Euler spring end connected to the mountingconnector.

Such embodiments may include a compensation system for altering one ormore angles of departure or for altering one or more constraints, ifpresent. An embodiment of a compensation system has a sensor thatdetects a characteristic related to motion (such as position, velocity,or acceleration), a compensator that provides an output that is at leastin part based upon a detection by the sensor, and an actuator that,responsive to the output provided by the compensator, alters at leastone of the first and second mounting connectors to change the angle ofdeparture associated with the Euler spring end connected to the mountingconnector.

In embodiments, the compensation system may be or may include a feedbacksystem. In an embodiment, the detection of the sensor is a measurementthat indicates a position of the payload and the feedback compensatorprovides a feedback output to the actuator using a position setpoint andthe measurement that indicates a position of the payload.

In embodiments, the compensation system may be or may include afeedforward system. In an embodiment, the characteristic related tomotion that the sensor detects is acceleration of a support structurethat supports an assembly comprising the payload mount and Euler springand the feedforward output provided by the feedforward compensator is atleast in part based upon an acceleration measurement detected by thesensor.

In embodiments, the compensation system may include both feedback andfeedforward systems. In embodiments, an adder sums the feedforwardoutput with the feedback output to obtain the output provided to theactuator.

In embodiments, one or more constraints may also be utilized in a systemthat alters one or more angles of departure. Such a system may accountfor constraint contact with an Euler spring when determining an outputfor the actuator. In embodiments, a compensation system may alter aconfiguration of a constraint.

Aspects of the present invention also include embodiments utilizing apayload supported in an inverted pendulum configuration by one or moreEuler springs that have one or more universal joint connections.

In embodiments, a system for reducing vibrations of a payload includes apayload connected to an Euler spring having a first end and a secondend. The first end of the Euler spring is connected to a mountingconnector of the payload and the second end connects to a secondmounting connector which is configured to connect to a supportstructure. The Euler spring supports the payload in an inverted pendulumconfiguration and the Euler spring is constructed to be in apost-buckled state that reduces vibrations of the payload by displacing.In this system, at least one of the first and second mounting connectorsis a universal joint. Such a system may include one or more additionalEuler springs. In embodiments, at least one Euler spring is connected tothe payload and is in a non-parallel configuration to the first Eulerspring. For example, in an embodiment, the second Euler spring may be ina horizontal configuration relative to the first Euler spring thatplaces the payload in an inverted pendulum position. In embodiments, oneor more constraints and/or one or more compensation systems may also beemployed in the system to help reduce vibration effects.

Some features and advantages of the invention have been generallydescribed in this summary section; however, additional features,advantages, and embodiments are presented herein or will be apparent toone of ordinary skill in the art in view of the drawings, specification,and claims hereof. Accordingly, it should be understood that the scopeof the invention shall not be limited by the particular embodimentsdisclosed in this summary section.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to embodiments of the invention, examples ofwhich may be illustrated in the accompanying figures. These figures areintended to be illustrative, not limiting. Although the invention isgenerally described in the context of these embodiments, it should beunderstood that it is not intended to limit the scope of the inventionto these particular embodiments.

FIG. 1A illustrates a cross sectional schematic view of a vibrationisolation system according to an embodiment of the invention.

FIG. 1B illustrates a vibration isolation system according to anembodiment of the invention.

FIG. 1C illustrates a vibration isolation system according to anembodiment of the invention.

FIG. 1D illustrates a vibration isolation system according to anembodiment of the invention.

FIG. 2 is a plot of Force (lbf) versus Displacement (inches) for asample metal spring blade for a vibration isolation system according toan embodiment of the invention. FIG. 2 also illustrates the shape of theblade for various forces.

FIG. 3A is a perspective view of a vibration isolation system accordingto an embodiment of the invention.

FIG. 3B is a line drawing of the embodiment depicted in FIG. 3A.

FIG. 4A is a perspective view of inner frame 120 with payload 150according to an embodiment of the invention.

FIG. 4B is the perspective view of inner frame 120, with the front rightsupport beam removed to show the pendulum structure according to anembodiment of the invention.

FIG. 4C is a line drawing of the embodiment depicted in FIG. 4A.

FIG. 4D is a line drawing of the embodiment depicted in FIG. 4B.

FIG. 5A illustrates an embodiment of a vibration isolation system inwhich the ends of the blades are fixed according to an embodiment of theinvention.

FIG. 5B is a line drawing of the embodiment depicted in FIG. 5A.

FIG. 6 illustrates two blades comprising lower ends having differentangles of departure from their mounting supports according to anembodiment of the invention.

FIG. 7A illustrates a constraint 700 according to an embodiment of theinvention.

FIG. 7B is a graph of displacement versus force for a blade 130 which isfirst free to deflect and then be constrained in its deflection by aconstraint 700 according to an embodiment of the invention.

FIG. 8 illustrates a vibration isolation system for a single degree offreedom system in which the angle of departure 600 of an Euler spring130 from its mounting connector is adjusted by an actuator 670 to varythe force the Euler spring exerts to address inertial forces when thesystem is mounted on a moving platform, according to an embodiment ofthe invention.

DETAILED DESCRIPTION

Systems and apparatuses for vibration isolation are described. In thiswritten disclosure, the term vibration (or vibrations) shall beconstrued to collectively and individually cover the various forms ofunwanted motions from vibration and shock. Also, one skilled in the artshall recognize that the term “isolation” as used, for example, in“vibration isolation system” refers to a system that helps minimizeunwanted motion. Because no system perfectly isolates unwanted motioneffects from a payload, references to vibration isolation or vibrationisolation systems shall not be construed to require complete isolation,but rather, shall be construed to encompass systems that reduce theeffects of unwanted motion on a payload.

For purposes of explanation, specific details are set forth in order toprovide an understanding of the invention. It will be apparent, however,to one skilled in the art that the invention can be practiced withoutthese details. Furthermore, one skilled in the art will recognize thatembodiments of the present invention, described below, may beimplemented in a variety of ways and constructed from a variety ofmaterials. Accordingly, the figures described below are illustrative ofspecific embodiments of the invention and are meant to avoid obscuringthe invention.

Reference in the specification to “one embodiment,” “a preferredembodiment” or “an embodiment” means that a particular feature,structure, characteristic, or function described in connection with theembodiment is included in at least one embodiment of the invention andmay also be in more than one embodiment. Also, the appearances of thephrase “in one embodiment” or “in an embodiment” in various places inthe specification are not necessarily all referring to the sameembodiment.

Components, or modules, shown in the figures are illustrative ofexemplary embodiments of the invention and are meant to avoid obscuringthe invention. It shall be understood that throughout this discussionthat components may be described as separate functional units, which maycomprise sub-units, but those skilled in the art will recognize that thevarious components, or portions thereof, may be divided into separatecomponents or may be integrated together. Furthermore, connectionsbetween components within the figures are not intended to be limited todirect connections. Also, additional or fewer connections may be used.In addition, signals between electrical components may be modified,re-formatted, or otherwise changed by intermediary components.

Many objects (such as, by way of example and not limitation, storagesystems, electronic devices, mechanical devices, electro-opticaldevices, instruments, tools, equipment, and other items) are sensitiveto undesired motions, which may affect the objects' performance,operation, lifespan, etc. However, there is often a desire to use suchitems in vibration-prone environments. For example, when operating diskdrives in an aircraft to store information, excessive vibrations withinthe aircraft can cause the disk drives to function at reducedperformance levels or to malfunction.

The present invention comprises systems and apparatuses that reduce thevibration experienced by a payload, which may be, by way of example andnot limitation, a storage system, an electronic device, a mechanicaldevice, an electro-optical device, an instrument, tool, equipment, andother item. The systems and apparatuses of the invention may be designedto isolate (which includes partially isolating) the payload from a rangeof vibration forces external to the system or apparatus. As a result,the motion of the payload is reduced, which allows the payload tooperate reliably for the range of vibration forces. One skilled in theart will recognize that the range of acceptable motion will vary for agiven payload.

FIG. 1A illustrates a cross-sectional schematic view of a vibrationisolation system according to one embodiment of the invention. As notedabove, the term vibration (or vibrations) shall be construed tocollectively and individually cover the various forms of unwantedmotions, including from vibration and shock. The reader is also remindedthat the “isolation” as used herein does not require perfectly isolationfrom unwanted motion. The vibration isolation system provides isolationof a payload against vibrations exerted in both the vertical andhorizontal directions. The system is comprised of an outer frame 110serving to support a payload 150 and an inner frame 120 that forms partof the structure that supports the payload relative to the supportingouter frame so that the payload can move relative to the outer frame.One skilled in the art will recognize that the outer and inner framesmay be constructed using a variety of materials, including but notlimited to, metal, plastic, and/or composites. For clarity, FIG. 1Ashows the constituent components of a two-dimensional system. Oneskilled in the art will readily be able to generalize this topology to athree-dimensional system. FIGS. 5A and 5B show a three-dimensionalrealization of the type illustrated in FIG. 1A.

In one embodiment of the invention, the weight of the inner frame 120and its payload 150 is supported within the outer frame by one or morespring blades 130. In FIG. 1A, two blades 130 are illustrated, one oneach side of payload 150. While only one blade is illustrated on eachside in this example, the invention is not so limited. A number ofblades may be employed on each side of the payload to achieve thedesired support conditions for the payload. Blades may be arranged tosupport the payload 150 and inner frame 120 so that inner frame 120 andpayload 150 are balanced with respect to their center of gravity orcenter of percussion. Further, multiple blades may be used in parallelto achieve the desired spring behavior.

In one embodiment, a blade is a thin strip of material with arectangular cross section. However, the invention is not limited toblades having a rectangular cross section. Rods with circular crosssections or other slender members with other shaped cross sections maybe used instead. One skilled in the art will recognize that the bladesmay be made of a number of materials, including but not limited tometal, plastic, or composites.

In one embodiment, the geometric and material properties of the blade(s)are selected such that when the payload 150 and inner frame 120 aresupported by the blade(s), the weight of the inner frame 120 plus thepayload 150 exceeds the critical force at which buckling of the blade(s)occur. For example, as illustrated in FIG. 1A, the weight of the payload150 and inner frame 120 are such that the blades 130 are buckled.

The buckling force for a slender compression element, a column, wasfirst analyzed by Leaonhard Euler and is called “Euler buckling.” Forthe case when both ends of the column are free to rotate, Euler bucklingoccurs when the critical force in the axial direction, P_(cr), of thecolumn exceeds P_(cr)=π²EI/L², where E is the modulus of elasticity, Iis the area moment of inertia and L is the length of the column. J.Winterflood and D. G. Blair at the University of Western Australia,Perth, noted that the force-displacement characteristics of columns justafter onset of buckling is spring-like for a useful range of motion andcoined the term Euler spring, which is discussed in Winterflood, J.,Blair, D. G. and Slagmolen, B., “High performance vibration isolationusing springs in Euler column buckling mode.” Physics Letters A, 300:pp. 122-130 (2002), which is incorporated by reference herein in itsentirety. Also incorporated herein by reference in their entirety are:Winterflood, J., T. A. Barber, and D. G. Blair, “Mathematical analysisof an Euler spring vibration isolator.” Physics Letters A, 300: pp.131-139 (2002); Winterflood, J., T. A. Barber, and D. G. Blair, “UsingEuler buckling springs for vibration isolation.” Classical and QuantumGravity, 19: pp. 1639-1645 (2002); John Winterflood, High PerformanceVibration Isolation For Gravitational Wave Detection (thesis presentedfor the degree of Doctor of Philosophy at the University of WesternAustralia, Department of Physics, 2001) LIGO-P020028-00-R. It shall benoted that herein the terms, blades, spring blades, and Euler springsare used interchangeably.

Since a buckled blade acts as a low-mass spring, it can be used toisolate against vibration and shock. Using one or more buckled blades,vibrations may be attenuated over a large range of frequencies,resulting in much lower vibration levels transmitted to the payload. Inthe configuration of FIG. 1A, the blades 130, when buckled, act assprings to isolate the inner frame 120 and payload 150 from much of thevibration forces acting in the vertical direction, which is in thedirection of the force applied to the blades 130 by the supportedpayload 150. As the outer frame 110 moves in the vertical direction as aresult of the vertical vibrations, the motion of the inner frame 120 andpayload 150 in the vertical direction is reduced significantly relativeto the vertical motion of outer frame 110.

FIG. 2 is a plot of the Force (lbf) versus Displacement (inches) for asample blade of spring steel that measures 0.015″×0.25″×6″. In thisexample, the end of the blade is pinned, which allows the blade to pivotas force is applied from the payload. Plotted is the displacement of theblade versus the axial force applied to it. The shape of the blade forvarious forces is also illustrated.

One skilled in the art will recognize that there are a number of ways toconnect the blades 130 to the payload and to a support structure. Inembodiments, the payload may be attached to a payload mount. Inembodiments, the inner frame 120 may function as a payload mount.Alternatively, the payload mount(s) may be integrated with the payload,for example, as depicted in FIG. 1B. It shall be noted that the payloadmay be directly connected to the payload mount or may be indirectlyconnected to the payload mount. For example, in FIG. 1A and FIG. 1C,inner frame 120 acts as payload mount in which a secondary vibrationisolation mechanism (pendulum 170) connects to the payload 150. Whereas,in the embodiment depicted in FIG. 1B, the payload mount may beconsidered to connect directly to the payload.

It shall also be noted that a number of items may function as supportmember. In embodiments, the outer frame 110 acts as the support memberor support structure. However, one skilled in the art shall recognizethat a chassis, table, platform, base, or other support member may beused. For example, in embodiments, one or more Euler springs may beconnected at one end to a payload via payload mounts and at the otherend to a support structure.

Furthermore, one skilled in the art will recognize that there are anumber of ways to connect the blades 130 to realize different endconstraints for the blades 130. One skilled in the art will recognizethat the shape of the blade 130 as it buckles in response to an axialforce applied to the blade 130 varies depending on the way in which theblade 130 is connected. The shape of a blade 130 as it bucklesinfluences the spring rate of the blade. For example, an end of blade130 may be free to rotate at the point of attachment/mounting connection(i.e. “pinned”), or it may be clamped rigidly (i.e. “fixed”).

In one embodiment, the blades 130 are connected to outer frame 110 andto railing 145 of the inner frame 120. In the embodiment illustrated inFIG. 1A, each end of the blade 130 is fixed to the outer frame 110 andthe inner frame 120. FIGS. 5A and 5B illustrate a realization of such anembodiment in which the ends of the blades 130 are fixed. Thisconfiguration leads to a lower natural resonance frequency, for the sameblade length, compared to configurations in which blade ends are pinned.As a result, the isolation becomes effective for vibrations at a lowerfrequency.

In an alternative embodiment, illustrated in FIG. 1C, each end of blade130 is pinned. FIG. 3A show an embodiment of this type of system. FIG.3B is a line drawing of the embodiment depicted in FIG. 3A.

In an alternative embodiment, the attachment of the blade ends on theinner frame may be fixed while the attachment of the blade on the outerframe may be pinned. Conversely, the attachment of the blade ends on theinner frame may be pinned while the attachment of the blade ends on theouter frame may be fixed.

One skilled in the art shall also recognize that one or morecombinations of the payload mounts, Euler springs, and supportstructures may be fabricated from a single item. For example, in anembodiment, an Euler spring and a support structure may be formed from asingle piece of plastic wherein a compliant mechanism hinge forms themounting connector between an end of the Euler spring and the supportstructure. Thus, it should also be noted that the mounting connectorneed not be limited to a separate component. One skilled in the art ofcomplaint mechanisms shall recognize any of number of ways to implementsuch configurations. Furthermore, it shall be noted that the teachingsof the present invention may be implemented in semiconductordevices/integrated circuits, such as for example, inMicro-Electro-Mechanical systems (MEMs). Accordingly, the payloadmounts, Euler springs, and/or support structures may be formed usingmaterials used in the fabrication of semiconductor devices/integratedcircuits.

In one embodiment, the spring rate can be tailored to increase as afunction of displacement. Non-linear spring behavior can be designed byconstraining the deflection of buckling members along loci ofdeflection. FIG. 7A illustrates a constraint 700 according to oneembodiment of the invention. As an increasing force is applied to theblade in a post-buckled state, the blade deflects until it comes intocontact with the constraint surface 700. During this displacement stage,the constraint 700 restricts the blades movement and reduces theeffective free length of the blade that acts as a spring. As theeffective length decreases, the spring rate increases. FIG. 7B is agraph of displacement versus force, and illustrates the two regions ordisplacement stages of blade deflection operation, namely, unconstrainedoperation before the blade contacts the constraint surface 700 andconstrained operation after the blade has contacted the constraintsurface. This can be an important design tool when designing vibrationisolation system for shock performance. In embodiments, it may bedesirable to increase the spring rate of the Euler spring as the payloadapproaches the limits of its sway space. This also allows multiplesprings to be combined in constructing a vibration isolation system thatfunctions in any orientation (i.e. in which the direction of gravity orcentrifugal force is not known or is variable).

Configuration of a constraint includes its position relative to a springblade, its shape, or both. Furthermore, one skilled in the art shallrecognize that constraints may be configured to increase or to decreasethe spring force of a spring blade. Also, it shall be noted thatmultiple constraints and multiple configurations of constraints may beemployed. For example, in an embodiment, a first constraint may contacta blade once a first displacement stage has been reached and a secondconstraint may contact the blade at a different location once a seconddisplacement stage. In embodiments, the first and second displacementstages may be the same stage.

In one embodiment, payload 150 is supported within inner frame 120 usingone or more pendulums. In the embodiment illustrated in FIG. 1A,pendulums isolate payload 150 from vibrations applied to the inner frame120 in the horizontal directions. Although two pendulums are illustratedin FIG. 1A, one skilled in the art will recognize that any number ofpendulums, including a single pendulum may be used to isolate payload150 from vibrations applied to the inner frame 120 in the horizontaldirections.

Each pendulum is comprised of a cable 170 that connects the uppersurface of inner frame 120 to payload 150. In this configuration, thepayload 150 is the weight of the pendulums. The pendulums isolatepayload 150 from horizontal vibrations applied to inner frame 120. Asthe inner frame 120 moves in the horizontal direction as a result ofhorizontal vibrations, the motion of payload 150 in the horizontaldirection is reduced significantly relative to the horizontal motion ofthe inner frame 120.

In one embodiment of the invention, secondary cable restraints 180 maybe connected from the payload 150 to the bottom surface of the innerframe 120. The secondary cable restraints 180 further constrain thedisplacement of the payload relative to the inner frame to the limits ofthe sway space between the inner frame 120 and the payload 150. In oneembodiment, secondary cable restraints 190 may also be used to furtherrestrain the displacement motion of inner frame 120 relative to theouter frame. The secondary cable restraints 190, illustrated in FIG. 1A,prevent the inner frame 120 from tilting or rotating within outer frame110.

FIG. 4A illustrates a perspective view of inner frame 120 with payload150 according to one embodiment of the invention. In this embodiment,the weight of payload 150 is supported within inner frame 120 by fourpendulums. Each pendulum is comprised of a cable 420 that is suspendedfrom the upper surface of inner frame 120 and wraps around or other wiseconnects to a portion of the payload 150. In this configuration, thepayload is the weight of the pendulum.

In one embodiment, the cable 420 wraps around a cylinder 450 protrudingfrom the payload 150 and is held in place by a screw 430. In oneembodiment cylinder 450 is made of a material, such as rubber thatprovides further vibration dampening. The pendulums isolate the payload150 from horizontal vibrations applied to inner frame 120 and allow thepayload 150 to be displaced relative to the inner frame 120 within thesway space between the payload 150 and the inner frame 120. As the innerframe 120 moves in the horizontal direction as a result of horizontalvibrations, the motion of the payload 150 in the horizontal direction isreduced significantly relative to the horizontal motion of the innerframe 120. In one embodiment, cable 420 further extends below theconnection point with the payload and is connected to the bottom surfaceof inner frame 120. This portion of cable 420 acts as a secondary cablerestraint which further constrains the displacement of the payload 150relative to the inner frame 120 to the limits of the sway space betweenthe inner frame 120 and the payload 150.

FIG. 4B is an illustration of the inner frame 120 from FIG. 4A, omittingthe support beam in the front right corner of the inner frame 120. Thisview shows the pendulum structure of the front right corner of the innerframe 120 which is used to support the payload 150. In one embodiment,each corner of the inner frame 120 comprises a similar pendulumstructure. The four structures function to support the payload andisolate payload 150 from horizontal vibrations.

FIGS. 3A and 3B illustrate a perspective view of a vibration isolationsystem according to one embodiment of the invention. In this embodiment,four blades 130 are used to support inner frame 120 within outer frame110. Two of the blades 130 are illustrated, while the two additionalblades 130 (not shown) are positioned out of view on the opposite sideof the vibration isolation system.

In one embodiment, the blades 130 are connected to railing 340 of outerframe 110. The blades 130 are also connected to railing 345 of the innerframe 120. One skilled in the art will recognize that there are a numberof ways to connect the blades 130 to the inner frame 120 and the outerframe 110. In one embodiment, railings 340 and 345 may comprise a numberof teeth in which the blades 130 may be recessed. The teeth in therailing provide flexibility in positioning the blades so they supportthe payload effectively through the center of gravity.

In an alternative embodiment of the invention, illustrated in FIG. 1B,blades provide both horizontal and vertical vibration isolation topayload 150. In one embodiment, blades 130 are attached to the outerframe 110 and to the payload mounts of the payload 150 with universaljoints 155. The ends of the blades 130 are fixed in the universal jointbut allowed to tilt in all directions. In this way, the blades 130function as inverted pendulums to isolate payload 150 from horizontaland vertical vibrations. Horizontal blades 135 and 136 stabilize thepayload 150 in the presence of horizontal vibrations, kinetic andgravitational forces that the payload 150 may be experiencing on amobile platform, for example, to keep payload 150 in a nominally uprightposition. When the payload 150 is in the upright position, the forceexerted by blade 135 cancels the force exerted by blade 136 and thepayload remains upright. If the payload inclines toward blade 135 due tohorizontal vibrations or because of the acceleration of the mobileplatform on which the system may be mounted, blade 135 will push thepayload back towards the upright position. Similarly, blade 136 restoresthe payload 150 to the upright position when the payload tilts towardblade 136.

In embodiments, a constraint surface 700 may be used to alter the springforce of blades 135 and/or 136 as a function of displacement so as toeffectively counteract the gravitational force or other forces that mayact to imbalance the inverted pendulum. As blade 135 or 136 deflects, itcomes into contact with the constraint surface 700. The surfacerestricts that blades movement and reduces the free length of the bladethat acts as a spring. This increases the spring rate of the spring andhelps to prevent the payload from coming into contact with outer frame110.

One skilled in the art will recognize that there are a number ofconfigurations of blades that may be used to support payload 150. In oneembodiment, blades may also be positioned in a similar mannerperpendicular to the plane of FIG. 1B to provide further isolation ofpayload 150 within outer frame 110.

FIG. 1D illustrates an alternative vibration isolation system accordingto one embodiment of the invention. In this embodiment, horizontalvibration isolation of payload 150 is accomplished through pendulums170A and 170B suspended from the outer frame 110 that are coupled to thepayload 150 through bell cranks 175A and 175B respectively. Bell cranks175A and 175B are coupled to payload 150 through at least one blade 130Aand 130B respectively. The bell cranks 175A and 175B also pivot aroundpivots 165A and 165B which are coupled to payload 150.

In one embodiment, the bell cranks 175A and 175B in combination withblades 130A and 130B, respectively, isolate the payload from vibrationsexerted in the vertical direction. The weight of the payload 150 createsa moment of force about pivot 165A. This force is countered by the bellcrank 175B in combination with blades 130B. Similarly, the weight ofpayload 150 creates a moment of force about pivot 165B, which iscountered by bell crank 175A in combination with blades 130A. Vibrationforces exerted in the vertical direction may increase or decrease themoment of force created by the weight of payload 150. Blades 130A and130B, when configured in a buckled state, act as springs to absorb thesevibration forces.

In the embodiment illustrated in FIG. 1D, the two blades 130 (the twoblades of 130A or the two blades of 130B) are buckled in opposingdirections and are coupled between the bell crank 175 and payload 150.As a blade starts to buckle, the direction of the offset deflection ofthe blade can be in one of two directions. When mounted in a pivotedsupport structure as shown in FIG. 1D, the effect of the offset of theblade in one direction is different from the effect of the offset of theblade in the opposite direction. For example, if the blade bucklestowards the pivot, then a low spring rate is obtained. If the bladebuckles away from the pivot, then a higher spring rate is obtained. Bymatching a pair of blades to buckle in opposing directions, the netspring rate of the two is closer to what would be obtained if it wererestrained to move linearly rather than in a rotating support structure.

One skilled in the art will recognize that alternative configuration ofthe bell cranks 175 and blades 130 are possible. For example, in oneembodiment, the bell crank configuration illustrated in FIG. 1D may beimplemented on each side of the payload 150. In an alternativeembodiment, the bell crank configuration may be implemented on opposingsides of the payload 150. In yet another alternative, bell cranks 175Aand 175B may be positioned on opposing sides of payload 150. One skilledin the art will also recognize that there are other ways of using leversto use the buckled blades so they are not inline with the gravitationalforce while they still isolate vibration in that direction.

In one embodiment, the spring rate of a blade may be changed byadjusting the angle of departure of the blade. For example, if the endsof a blade are clamped or fixed at an angle, as opposed to beingextending vertical from its mount, the force supported by the bladedecreases. FIG. 6 illustrates two sample blades 530 and 540, which havedifferent angles of departure. The ends of blade 530 are fixedperpendicular to railings 550 and 560 respectively. By contrast, theangle of departure for the bottom end of blade 540 has been adjusted byan angle α away from perpendicular. By changing the angle of departure,the force supported by the blade 540 is decreased compared to the forcesupported by blade 530.

One skilled in the art will recognize that there are a number of ways tochange the angle of departure of a blade. In the embodiments describedpreviously in which the ends of a blade are recessed into teeth in arailing, the angle of departure for one end of a blade may be adjustedby simply recessing one end of the blade in-between a different set ofteeth within the rail while leaving the opposite end of the blade in thesame location. As another example, when using fixed blades, the clampthat fixes the blade to a surface may be angled relative to the surfaceto alter the angle of departure of the blade.

The angles of departure of the blade, at one or both of its mountingpoints, may be adjusted dynamically to vary the force applied to thepayload in order to meet specific performance objectives. For example,when the vibration isolation system is installed on an aircraft,inertial forces must act on the payload during aircraft maneuvers suchas takeoffs, landings and turns in order to move the payload along thetrajectory of the aircraft. In other words, the payload must beaccelerated with the aircraft, and in order to do so, forces must beapplied to the payload. These forces may be allowed to act on thepayload in a controlled manner by adjusting the angle of departure ofthe blade. The force which a blade exerts on the payload may beregulated with a compensation system, such as, by way of example and notlimitation, a servo-controlled system. FIG. 8 illustrates a vibrationisolation/absorption system for a single degree of freedom system,according to an embodiment of the invention. For clarity, FIG. 8 depictsthe system only regulating motion in the vertical direction; however,the principles are readily extended to regulating motion in additionaldegrees of freedom. In FIG. 8, the payload may be configured the same asor similar to the embodiment depicted in FIG. 1B.

In the embodiment depicted in FIG. 8, the position 610 of the payload150 relative to the outer frame 110 is detected. The angle of departure600 of the end of the blade 130 fixed to the outer frame 110 is adjustedby an actuator, which in the depicted embodiment is a motor 670, toregulate this detected position 610 around the position setpoint 620.The position setpoint would typically be in the center of the swayspace. One skilled in the art shall recognize that any of number ofactuators may be employed, included by way of example and notlimitation, piezoelectric, voice coils, motors, pneumatics, hydraulics,and the like, and that no particular actuator is critical to the presentinvention. One skilled in the art shall also recognize that it may alsobe advantageous to detect acceleration or velocity of the payload anduse the detection to regulate the payload position. It shall be notedthat position, velocity, and acceleration are characteristics related tomotion. Accordingly, embodiments of the present invention may includeone or more sensors that detect one or more characteristics related tomotion. One skilled in the art shall recognize that detecting acharacteristic related to motion may be accomplished by measuring one ormore of position, velocity, and acceleration.

The feedback compensation 640 shapes the loop dynamics. The loopdynamics would typically be adjusted to allow the payload to follow thelow-frequency trajectory dynamics of the mobile platform to which theouter frame 110 or other spring supporting structure is attached—in thisexample the aircraft—while not tracking high-frequency vibrations—inthis example the structural vibrations of the airframe. If the loopbandwidth of the compensation system includes the natural resonance ofthe payload/blade system, it will actively damp the payload. Thefeedforward compensation 650 would typically be designed so that theforce applied by the Euler spring 130 to the payload 150 is commensuratewith the inertial forces caused by the motion of the platform the outerframe 110 or other spring supporting structure is attached to. Inpractice, the signal producing the acceleration reference 630 wouldtypically be produced by an accelerometer attached to the outer frame orother spring supporting structure, measuring the acceleration of themobile platform. One skilled in the art shall understand that thecompensation system may be implemented using servo design theory and thelike. One skilled in the art shall also recognize that no particularimplementation of either the feedback compensator 640 or the feedforwardcompensator 650 is critical to the present invention. Accordingly,either or both systems may be analog or digital, the feedbackcompensator may implement one or more modes of proportional, integral,and derivative (PID) control, or other type of control.

One skilled in the art shall recognize that a vibration isolation systemthat includes a compensation system may include feedback compensation,feedforward compensation, or both. Furthermore, one skilled in the artshall recognize that the active control provided by a compensationsystem may be applied to other elements of the system, including withoutlimitation, to the number of constraints, the position of theconstraints, the topology of a constraint, and to any of the mountingpoints in the system. In embodiments, a constraint may be actively usedto adjust an angle of deflection of an Euler spring by effectivelyaltering an end condition of the spring.

While the present invention has been described with reference to certainembodiments, those skilled in the art will recognize that the inventionis not limited to the specific embodiments discussed. For example,though many of the embodiments illustrate single blades in a buckledstate, one skilled in the art will recognize that multiple blades couldbe used in parallel or in opposing buckled states to achieve desiredspring rates. Variations upon and modifications to the embodiments areprovided for by the present invention.

1. A system for reducing vibrations of a payload, the system comprising: a payload mount; a Euler spring having a first end and a second end opposite the first end, the first end connected to the payload mount and the second end configured to be connected to a supporting structure, the Euler spring constructed to be in a post-buckled state that reduces vibrations of a payload attached to the payload mount by displacing; and a constraint configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a displacement stage of the Euler spring.
 2. The system of claim 1 wherein the constraint is a first constraint and the system further comprises: a second constraint configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a second displacement stage of the Euler spring; and wherein the second constraint contacts the Euler spring at a location between the first and second ends of the Euler spring that is different from that contacted by the first constraint.
 3. The system of claim 1 wherein the constraint produces a non-linear spring behavior in the Euler spring.
 4. The system of claim 1 further comprising a compensation system comprising: a sensor that detects a characteristic related to motion; a compensator that provides an output that is at least in part based upon a detection from the sensor; and an actuator that, responsive to the output provided by the compensator, alters a configuration of the constraint.
 5. The system of claim 4 wherein the configuration of the constraint that is altered is its position relative to the Euler spring.
 6. The system of claim 4 wherein the constraint alters an angle of departure of at least one of the first and second ends of the Euler spring.
 7. A system reducing vibrations of a payload, the system comprising: a payload mount connected to a first mounting connector; and an Euler spring having a first end and a second end opposite the first end, the first end of the Euler spring connected in a fixed position relative to the first mounting connector that forms a first angle of departure of the Euler spring, and the second end connected in a fixed position relative to a second mounting connector that forms a second angle of departure of the Euler spring, the Euler spring constructed to be in a post-buckled state that reduces vibrations of a payload attached to the payload mount by displacing, and at least one of the first and second mounting connectors is controllably alterable to change the angle of departure associated with the Euler spring end connected to the mounting connector.
 8. The system of claim 7 further comprising a compensation system comprising: a sensor that detects a characteristic related to motion; a compensator that provides an output that is at least in part based upon a detection by the sensor; and an actuator that, responsive to the output provided by the compensator, alters at least one of the first and second mounting connectors to change the angle of departure associated with the Euler spring end connected to the mounting connector.
 9. The system of claim 8 wherein the compensation system comprises a feedback system comprising: a feedback compensator that provides a feedback output that is at least in part based upon a detection by the sensor and wherein the output provided to the actuator is, at least in part, based upon the feedback output.
 10. The system of claim 9 wherein the detection of the sensor is a measurement that indicates a position of the payload and the feedback compensator provides a feedback output to the actuator using a position setpoint and the measurement that indicates a position of the payload.
 11. The system of claim 8 wherein the compensation system further comprises a feedforward system comprising: a feedforward compensator that provides the output that is at least in part based upon a detection by the sensor.
 12. The system of claim 11 wherein the characteristic related to motion that the sensor detects is acceleration of a support structure that supports an assembly comprising the payload mount and Euler spring and wherein the feedforward output provided by the feedforward compensator is at least in part based upon an acceleration measurement detected by the sensor.
 13. The system of claim 9 wherein the compensation system further comprises a feedforward system comprising: a feedforward sensor that detects a characteristic related to motion a support structure that supports an assembly comprising the payload mount and Euler spring; a feedforward compensator that provides a feedforward output that is at least in part based upon a detection by the feedforward sensor; and wherein the compensator comprises an adder that sums the feedforward output with the feedback output to obtain the output provided to the actuator.
 14. The system of claim 7 further comprising: a constraint configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a displacement stage of the Euler spring.
 15. The system of claim 14 wherein the output provided to the actuator is determined at least in part by whether the Euler spring contacts the constraint surface.
 16. The system of claim 14 further comprising: a constraint compensator that provides an output that is at least in part based upon a detection from a sensor; and a constraint actuator that, responsive to the output provided by the constrain compensator, alters the position of the constraint.
 17. A system for reducing vibrations of a payload, the system comprising: a payload having a first mounting connector; an Euler spring having a first end and a second end opposite the first end, the first end of the Euler spring connected to the first mounting connector and the second end connected to a second mounting connector which is configured to connect to a support structure, the Euler spring supporting the payload in an inverted pendulum configuration and the Euler spring constructed to be in a post-buckled state that reduces vibrations of the payload by displacing; and wherein at least one of the first and second mounting connectors is a universal joint.
 18. The system of claim 17 wherein the Euler spring is a first Euler spring and the system further comprises at least one Euler spring connected to the payload that is in a non-parallel configuration to the first Euler spring.
 19. The system of claim 17 further comprising: a constraint configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a displacement stage of the Euler spring.
 20. The system of 17 further comprising a compensation system comprising: a sensor that detects a characteristic related to motion; a compensator that provides an output that is at least in part based upon a detection by the sensor; and an actuator that, responsive to the output provided by the compensator, alters at least one of the first and second mounting connectors to change an angle of departure at which the associated Euler spring end extends from the connected mounting connector. 